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iSCSI: Set up and use LIO targets

Hands-On Storage

Article from ADMIN 26/2015

By Michael Schuler

The LIO multiple-protocol SCSI target is perfectly suited for complex test environments, especially because of its support for SCSI standards across the board.

Currently, three network technologies dominate the SAN: Fibre Channel (FC), iSCSI, and Fibre Channel over Ethernet (FCoE). Of the three, only iSCSI can be set up in a standard LAN without much effort. In contrast, FCoE necessitates changes to Ethernet, and Fibre Channel even needs a different network. iSCSI, however, just tunnels SCSI commands over standard TCP connections and can thus be routed over IP like many other protocols.

This means that iSCSI is not just a cheap alternative to the previously dominant Fibre Channel but is also very useful when you need to stage test systems. For example, you can simulate a storage rack with a virtual machine by installing a suitable iSCSI target on the virtual machine's operating system. I will look at exactly that use case in this article, with a special focus on hands-on implementation.

Until 2011, iSCSI Enterprise Target (IET) was the standard SCSI target in the Linux kernel [1]. It was then replaced by LIO (which is a brand name by Datera Inc.; see the Linux SCSI Target wiki [2] for more details). The wider support for various SCSI standards was a major improvement, in particular Asymmetric Logical Unit Assignment (ALUA) and SCSI-3 Persistent Reservations [3]. I will be returning to the latter later in the article.

LIO has been covered previously in Linux Magazine [4], but this article looks into the configuration options with the help of the lio-utils . These tools have been replaced with the newer targetcli , and I will look at how to install and manage this tool.